The Royal College of Surgeons said patients were forced to put on more weight or develop life-threatening complications in order to qualify for the National Health Service (NHS) to pay for stomach-contracting surgery.

Weight loss specialists meeting at the college said the restrictions were "unfair and unethical."

Under the NHS Constitution, patients have a legal right to be assessed for weight loss surgery if their Body Mass Index (BMI) is 40 or higher.

But in some parts of Britain, doctors only consider operating on patients with a BMI of 50 or 60.

"In many regions the criteria are being raised to save money," said surgeon and professor Mike Larvin. "Patients are being denied life-saving and cost-effective treatments and effectively encouraged to eat more in order to gain a more risky operation down the line."

Patients lose 70 percent of their excess weight within 18 months of the surgery, curing almost all cases of diabetes.

Although the operation costs $16,000, studies indicated that the bill for treating the medical complications of obesity were so high that the surgery paid for itself within three years.

Around 240,000 severely obese Britons want the operation, a number too high for the NHS to handle. A lottery introduced to manage demand meant that last year only 4,300 had their surgery paid for by the taxpayer-funded NHS.

Chair of the National Obesity Forum Dr. David Haslam said, "Even the most cynical taxpayer should support (weight loss) surgery, alongside clinicians, opposing the unethical and immoral barriers to surgery imposed by NHS purse-string holders."

The Department of Health said surgery should only be used as a last resort once diet and lifestyle changes failed.